Method of infiltrating powder metal parts



Feb. 26, 1957 A. BOYCE 2,783,145

METHOD OF INFI-LTRATING POWDER METAL PARTS Filed May 22, 1952 1/ C160 /5A T 2 6 i i W I Eeeous 279/7040 l.- flare:

Riff; Z INVENTOR.

4mm OF INFILTRATING POWDER METAL PARTS Application May 22, 1952, Serial No. 289,271

4 Claims. c1. 75-212 This invention relates to an impregnating method for infiltrating cupreous metal into porous ferrous parts and is "particularly concerned with a method of infiltration wherein pitting and channeling of the ferrous part, due to the dissolving action of the cupreous metal, is entirely eliminated.

,'It is, therefore, the prime object of the invention to provide 'a method for impregnating ferrous parts with cupreous metal wherein the dissolving action of the cupreous metal for iron is entirely satisfied at the temperature ofiimpregnation and prior to the time that the cupreous metal contacts the porous ferrous part.

. .A still further object of the invention is to provide a inethodforinfiltrating porousferrous parts with cupreous metal wherein the infiltration may be carried out simultaneously with the sintering of the ferrous part.

-Another object of the invention is to provide a method for infiltrating porous ferrous parts with cupreous metal wherein the cupreous metal is maintained out of contact with the porous ferrous part until such infiltrant becomes molten and wherein sufficient iron or; ferrous material is included with the cupreous metal to satisfy its full dissolving action for iron at the temperature of infiltration. After the cupreous metal has become molten and has fully satisfied, its dissolving action for iron, the molten impregnant is permitted to contact the part to be. in-

States Patent O In carrying out this object, it is a further object to provide a mold or crucible including valvingmeansfor holding the cupreous metal with a ferrous addition away from the part to be impregnated until such time that the cupreous metal is molten and has satisfied itsdissolving action for iron whereupon the valve in connection with the mold oi crucible is opened and the molten'cupreous metal "is allowed to contact the porous ferrous part to be infiltrated.

Further objects and advantages of the present invention will'be apparent from the following description, reference being had to the accompanying drawing, wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

Fig. l is a diagrammatic showing of one type of mold which may be used in carrying out the method disclosed herein, the mold being shown with the valve closed.

Fig. 2 is a view of the same mold as shown in Fig. 1 wherein the valve is shown in open position.

In the past, several methods have been proposed for reducing and/or eliminating channeling and pitting of porous ferrous parts during impregnation thereof with copper or other cupreous metals.

Bourne, Patent No. 2,401,221, suggests mixing iron powder with the copper or cupreous alloy prior to its disposition on the iron whereupon the entire assembly is heated in excess of the melting point of the cupreous metal which melts, dissolves a portion of the iron powder, and fiows into the pores of the porous ferrous article.

2,783,145 Patented Feb. 26, 1957 If substantial impregnation is to be carried out by this method some dissolving or pitting action may still be in evidence unless the cupreous metal is carefully disposed and all conditions of operation are controlled.

In application, Serial No. 156,619, now Patent No. 2,606,831, dated August 12, 1952, the problem is attacked in a different manner whereby the cupreous material is placed in a crucible of porous iron or on a gate of porous iron attached to the article where, after melting, the cupreous material runs through the crucible or into the gate, dissolves a portion thereof and then runs into the article to be impregnated. This method is highly satisfactory in that all of the pitting and channeling, due to dissolving action, occurs in the part which is removed. However, in many instances, it is difficult or impractical to provide a gate on the part to be impregnated. Also the crucible is erroded to a point that replacement is required. The present invention eliminates these difiiculties through the use of a mold formed from. graphite-for example,- which mold is shown at 20. The part to be impregnated is shown at 22 and is connected to the main mold body by a plurality of ducts 2.4. A valve 26 closes the ducts and, in the diagrammatic showing, includes an operating plunger 28 thereon. The impregnating. material, such as copper or cupreous alloy mixed with the required quantity of iron powder to completely satisfy the dissolving action, is disposed in the upper portion 34) of the mold at 32. The mold 20, with the part to be impregnated thereunder, is then passed through a furnace wherein it is heated to a suitable temperature at least in excess of the melting point of the cupreous material to be impregnated into the part. During the heating, the impregnating material 32 becomes molten and dissolves sufiicient iron to satisfy its dissolving action for iron at the temperature of operation and is held in-t he upper part'of the mold. As the mold passes through the furnace',--preferably on a conveyor, the rod 28 is disposed so as to engage 'a stop or other device 29, as shown in Fig. 2, which tips the valve to open the ducts24- whereby the impregnating material 32, in the molten'state, flows through the ducts and into the part'22 to be impregnated whereupon it is distributed uniformly by capillarity within the porous structure thereof" 5 1 I Y After: the 'conveyor has carried the ma 28 past the stop, the valve'26'rights itself and the mold may then emerge from the furnace whereupon the impregnated part may be separated therefrom.

In the present instance, it is quite apparent that the part to be placed under the mold 20 may be in the green state whereupon sintering of the part is accomplished as it passes through the furnace at the same time that the impregnating material is being rendered molten. In this .instance, the furnace temperature must be sufiicient to cause sintering, for example, with parts made from substantially pure iron powder, a temperature of from 2000" to 2050" F. has been found satisfactory. This of course is well above the melting point of the cupreous material which may be pure copper, copper with manganese, copper with tin, copper with nickel, etc., all alloys being capable of being used alone or in combination, in each instance, the sintering temperature being sufiicient to melt the impregnating metal.

If alloys of iron are used in the part, sintering temperatures, suitable for the operation in view of the specific composition of the article, should be chosen. It is to be understood that it may be desirable to utilize a nonoxidizing atmosphere in the furnace to prevent or reduce oxidation. In some instances, this may not be necessary, however it is preferred.

By following the teachings of this invention, it is apparent that simultaneous sintering and impregnation may be carried out wherein the copper or cupreous alloy has ferrous material added thereto in quantities sufficient to completely satisfy the dissolving action of copper for iron at the temperature of impregnation which is an important factor in avoiding and eliminating'pitting or channeling of the part to be impregnated. It is also understood that the quantity of cupreous material placed in the mold 20 is predetermined so as to accomplish any desired degree of impregnation from a partial impregna tion to a complete impregnation as is desired.

It is evident in the present process that the ferrous part is brought to the impregnating temperature before the impregnant is allowed to contact with it. In this manner, the impregnant is not in contact with the ferrous part any substantial length of time since the impregnated part may be cooled substantially immediately after the molten impregnant has been allowed to contact it. This reduces the tendency towards dimensional change, prevalent during infiltration operations.

This is explained by the fact that the heated ferrous part soaks up the impregnant immediately rather than by a gradual infiltration thereof as often experienced when using other processes. Further, the part is fully sintered when impregnated with all bonds established between adjacent particles even when simultaneous sintering and infiltration are being carried out.

It is further manifest that the cupreous metal impregnant may be supplied with iron or ferrous alloy in any other suitable manner, such as, mixing metal powders, or mixing the metals in the molten state and casting them into slugs, etc. The iron may also be added by including a porous iron ring or lining in the crucible from which iron will be dissolved by the molten cupreous metal as needed, wherein the iron part is replaced periodically. In this case, the quantity of iron is not critical since any iron not dissolved by the copper will remain in the crucible. In my copending application Serial No. 289,272, filed concurrently herewith, the method of sintering and simultaneously impregnating various metals and alloys is discussed.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a method for infiltrating a porous ferrous part with cupreous metal wherein pitting and channeling is entirely eliminated, the steps comprising; providing a predetermined quantity of cupreous metal mixed with sufficient iron to completely satisfy the dissolving action of the copper for iron at the temperature of infiltration, superimposing the cupreous metal with the iron associated therewith in a separate zone immediately adjacent and above the porous ferrous part to be infiltrated, heating simultaneously the porous ferrous part and the cupreous metal with the iron associated therewith under the same environment and to a temperature above the melting point a time sufiicient to cause the cupreous metal to become molten and to dissolve sufiicient of the iron associated therewith to completely satisfy the dissolving action of copper for iron at the environment temperature, and then flowing the molten cupreous metal with the iron dissolved therein into contact with the heated porous ferrous part to be impregnated whereupon the cupreous metal is drawn into the porous ferrous part by capillarity without pitting or channeling the ferrous part.

2. The method as claimed in claim 1 wherein the heating step is carried out for a time sufficient to simultaneously sinter the porous ferrous part.

3. In a method for infiltrating a porous ferrous part with cupreous metal wherein pitting and channeling is entirely eliminated, the steps comprising; positioning a suitable quantity of cupreous metal mixed with sufiicicnt iron to satisfy the dissolving action of copper for iron at the temperature of infiltration, above the porous errous part to be infiltrated and in superimposed isolated zones with channeling means therebetween, heating simultaneously the porous ferrous part and the cupreous metal with the iron associated therewith under the same condition of environment and in said isolated zones to a tem perature above the melting point of the cupreous metal and below the melting point of the porous ferrous part, maintaining said temperature for a time sufficient to cause the cupreous metal to become molten and to dissolve sufficient of the iron associated therewith to completely satisfy the dissolving action of copper for iron at the environment temperature, and then flowing the molten cupreou metal through said channeling means into contact with the heated porous ferrous part to .be impregnated whereupon the cupreous metal is drawn into the porous ferrous part without channeling or pitting of the porous ferrous part.

4. The method as claimed in claim 3 wherein the heating step is carried out for a time sufiicient to simultaneously sinter the porous ferrous part.

References Cited in the file of this patent UNITED STATES PATENTS 1,026,429 Coolidge May 14, 1912 1,053,880 Scott Feb. 18, 1913 1,511,063 Pack Get. 7, 1924 2,401,221. Bourne May 28, 1946 2,422,439 Schwarzkopf June 17, 1947 2,456,779 Goetzel Dec. 21, 1948 2,518,253 Reis Aug. 8, 1950 2,561,579 Lenel July 24, 1951 2,606,831 Koehring Aug. 12, 1952 FOREIGN PATENTS 148,533 Great Britain Sept. 8, 1921 

1. IN A METHOD FOR INFILTRATING A POROUS FERROUS PART WITH CUPEROUS METAL WHEREIN PITTING AND CHANNELING IS ENTIRELY ELIMINATED, THE STEPS COMPRISING; PROVIDING A PREDETERMINED QUANTITY OF CUPREOUS METAL MIXED WITH SUFFICIENT IRON TO COMPLETELY SATISFY THE DISSOLVING ACTION OF THE COPPER FOR IRON AT THE TEMERATURE OF INFILTRATION, SUPERIMPOSING THE CUPREOUS METAL WITH THE IRON ASSOCIATED THEREWITH IN A SEPARATE ZONE IMMEDIATELY ADJACENT AND ABOVE THE POROUS FERROUS PART TO BE INFILTRATED, HEATING SIMULTANEOUSLY THE POROUS FERROUS PART AND THE CUPREOUS METAL WITH THE IRON ASSOCIATED THEREWITH UNDER THE SAME ENVIRONMENT AND TO A TEMPERATURE ABOVE THE MELTING POINT OF THE CUPREOUS METAL AND BELOW THE MELTING POINT OF THE POROUS FERROUS PART, MAINTAINING SAID CONDITIONS FOR A TIME SUFFICIENT TO CAUSE THE CUPREOUS METAL TO BECOME MOLTEN AND TO DISSOLVE SUFFICIENT OF THE IRON ASSOCIATED THEREWITH TO COMPLETELY SATISFY THE DISSOLVING ACTION OF COPPER FOR IRON AT THE ENVIRONMENT TEMPERATURE, AND THEN FLOWING THE MOLTEN CUPREOUS METAL WITH THE IRON DISSOLVED THEREIN INTO CONTACT WITH THE HEATED POROUS FERROUS PART TO BE IMPREGNATED WHEREUPON THE CUPREOUS METAL IS DRAWN INTO THE POROUS FERROUS PART BY CAPILLARITY WITHOUT PITTING OR CHANNELING THE FERROUS PART. 